Inter-cell power control for interference management

Abstract

A system and method for inter-cell power control for interference management in an OFDM system is provided. The system provides for a combination use of open loop and closed loop PSD control algorithms. The open loop control is a function of path loss from the serving cell as well as the neighboring cells. The closed loop control updates the end node transmit PSD by listening to the load indicators from the serving cell and at least one other neighboring non-serving cell which generates the highest level of interference. The system thus provides a fast and tight control with multi-cell information that allows improved inter-cell interference control.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent application Ser. No. 60 / 863,928 entitled “Method And Apparatus For Inter-Cell Power Control For Interference Management” which was filed Nov. 1, 2006. The entirety of the aforementioned application is herein incorporated by reference.BACKGROUND[0002]I. Field[0003]The following description relates generally to wireless communications, and more particularly to inter-cell power control for interference management in an OFDM system.[0004]II. Background[0005]Typical load control scenarios focus either on closed loop or open loop controls. There are limited views on incorporating both types of loop control. In non-orthogonal systems, methods involving both type of loop control are geared to spread spectrum time division systems and are aimed at single cell applications. In orthogonal systems, there are two main schools of thought as to uplink interference control. One camp favors a ...

AI Technical Summary

Benefits of technology

[0012]In orthogonal systems, inter-cell interference often drives inefficiency of a multi-cell system. An aspect of the claimed subject matter provides for a control method that listens to more than one cell's load commands. This allows an end node to overcome a typical limitation of a serving cell not being aware of interference caused by transmission of its terminals to other cells.

[0014]With an orthogonal uplink, in a single cell scenario, a UE may transmit at maximum Tx power without impacting the link performance of other users. In a multi-cell scenario, with such a strategy, UEs at cell edge inject significant interference into other cells, diminishing the system coverage. However, cell interior UEs typically do not cause interference in other cells. For a stable and optimal system operation, we observe that cell interior UEs may transmit at higher power or power spectral density, than the UEs at cell edges. Therefore, we keep two objectives in mind for an UL interference management algorithm: 1) means to reduce inter-cell interference and 2) scheduler flexibility to allocate bandwidth to different users. Further, conventional assumptions may include that each UE has a single serving cell in the uplink and that the serving cell is typically not aware of the interference caused by the transmission from its terminals to the other cells.

[0016]Another aspect provides for permitting scheduler flexibility in reducing inter-cell interference. A scheduler for each cell has flexibility to allocate variable bandwidth and power spectral density (PSD) to end nodes in its domain. The scheduler can allow higher transmit power usage for end node's in cell centers where that greater power usage does not cause interference with other cells.

[0017]Another aspect provides for a method of using both open and closed loop controls. By first employing an open loop PSD control at the beginning use of end node accuracy concerns of the closed loop process are alleviated. Once an initial target value is established, control is switched to the closed loop method, and errors and uncertainties associated with the open loop process are mitigated.

[0019]An aspect provides for a method that facilitates inter-cell interference control in an OFDM system, comprising: using a target Rxed which utilizes path loss readings from both end node to serving node and from end node to neighboring non-serving nodes; using open loop PSD control at the onset of end node use or at a large change in end node path loss function; and switching to closed loop PSD control at an appropriate time.

Problems solved by technology

In orthogonal systems, inter-cell interference often drives inefficiency of a multi-cell system.

The 5% user data throughput is not the adequate metric to dictate the true coverage of the system due to the benefit from HARQ and link adaptation on the UL shared data channel.

In a multi-cell scenario, with such a strategy, UEs at cell edge inject significant interference into other cells, diminishing the system coverage.

Further, conventional assumptions may include that each UE has a single serving cell in the uplink and that the serving cell is typically not aware of the interference caused by the transmission from its terminals to the other cells.

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